1. Field of the Invention
This invention relates to lawn mowers of the type having a housing with a cutting blade mounted on a shaft journalled for rotation in the housing and, more particularly, to a clamp assembly which can be used to limit rotation of the cutting blade, as to facilitate safe handling of the blade during assembly, disassembly and reconditioning thereof. The invention is also directed to a method of using the clamp assembly.
2. Background Art
Elongate cutting blades are used on a wide range of lawn mowing equipment. One typical lawn mower construction utilizing an elongate blade has a fixed housing mounted on wheels and manipulated through a push-type handle. The housing defines a cutting chamber within which a cutting blade is mounted. The cutting blade is mounted on a shaft which is journalled for rotation in the housing.
In another construction, decks, with one or more cutting blades, are mounted on a vehicle, such as a tractor. The deck has a housing with at least one chamber for a cutting blade. On decks having multiple blades, typically each cutting blade is mounted upon a shaft on the housing that projects upwardly therethrough to allow a pulley to be mounted on the shaft. One or more belts can be used to engage the pulleys and simultaneously drive the shafts and the cutting blades thereon.
Periodically, cutting blades need to be accessed to effect removal and/or reconditioning thereof. In a typical blade mount, the shaft has an enlarged fitting on the end which accommodates one or multiple bolts. A blind bore on the fitting has an axis that is coincident with the rotary axis for the shaft. Two diametrically opposite through bores are provided to accept a like number of bolts to prevent rotation of the blade relative to the fitting around the shaft axis.
There are a number of dangers associated with cutting blade maintenance. The cutting blade is free to rotate about the shaft axis during this maintenance. By attempting to tighten or loosen the mounting bolts, an individual may inadvertently rotate the cutting blade around the axis of the shaft. This could cause inadvertent and harmful contact between the cutting blade and the individual.
Often, individuals securing or removing a cutting blade may directly grasp the cutting blade with one hand while manipulating a wrench with the other hand. A torque exerted, principally upon the center bolt which coincides with the shaft axis, tends to rotate the shaft and the cutting blade. If the user exerts a substantial torque on the wrench, the hand holding the blade may be cut thereby.
Aside from the physical dangers, the individual holding the blade may not be able to hold the blade with sufficient force to allow the bolts to be properly tightened or loosened.
A more serious problem is that a torque applied to the cutting blade may cause inadvertent ignition of the engine driving the cutting blade, with potentially severe consequences.
To address these problems, various mechanisms have been devised for limiting rotation of a cutting blade relative to a deck/housing. Examples of these structures are shown in each of U.S. Pat. Nos. 4,564,991 (Taylor); 4,208,859 (Brockway); 5,865,018 (Wanie); 3,173,234 (Vodinelich); and 4,882,960 (Kugler).
In U.S. Pat. No. 4,956,905 (Davidson) a structure is shown for allowing a user to exert a force to limit rotation of the cutting blade without directly contacting the cutting blade.